Perhaps "what are you searching for?" Messages posted and available to read through that interface will be to and from your Google Contacts. (That's the people you Gmail with, basically.) Google is making a big push for people to take their Google Profiles more seriously and one consequence of that could be a well populated social graph for users.
Friends could help answer the questions you're asking of Google or they could let you know what they are doing, like a home town version of Google News.
Image search challenge: Develop a robust way of understanding user intent from a given query and generate highly relevant image clusters that match with the intent so that more images can be surfaced to searchers. We are also looking for interesting presentation methods that will help searchers navigate these image clusters easily.
W. Xi, E. Fox, W. Fan, B. Zhang, Z. Chen, J. Yan, and D. Zhuang. SIGIR '05: Proceedings of the 28th annual international ACM SIGIR conference on Research and development in information retrieval, page 130--137. New York, NY, USA, ACM, (2005)
M. Strohmaier, M. Lux, M. Granitzer, P. Scheir, S. Liaskos, and E. Yu. We Know'07 International Workshop on Collaborative Knowledge Management for Web Information Systems, in conjunction with WISE'07, Nancy, France, (2007)